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Publication History:
This article was written
especially for "Crain's Petrophysical Handbook"
by E. R. Crain,
P.Eng in 202.
This webpage version is the copyrighted intellectual
property of the author.
Do not copy or distribute in any form without explicit
permission. |
HYDROGEN BASICS
Hydrogen is the smallest and
lightest element. At standard conditions hydrogen is a
diatomic gas (H2). It is colorless, odourless, tasteless,
non-toxic, and highly combustible, creating water (H2O) when
burned. Hydrogen can be separated from water by electrolysis
and from methane by pyrolysis or steam reforming. There is
one known example of naturally occurring hydrogen in a
reservoir setting, but dozens of hydrogen seeps are known
around the World.
Most of the hydrogen on Earth exists in water
and organic compounds. Known occurrences of natural hydrogen are
rare, partly because we haven’t looked very hard due to preconceived
opinions that are probably wrong.
Major uses of hydrogen are upgrading bitumen
and heavy oil, and removal of sulphur from liquid petroleum. The use
of hydrogen for lighter than air transportation was abandoned in
1937 after the dirigible Hindenburg caught fire. There are 1000s of
other commercial uses in food preparation, plastics, and
petrochemicals.
Hydrogen may be the wave of the future for
powering land transportation and industry in the “Hydrogen Economy”
– think 2050 or beyond. There are many unresolved technical and
practical issues. The virtue of such a fuel is that the exhaust is
water (and maybe some NOx) instead of CO2, which contributes to
climate change. The exhaust water would have to be captured on the
vehicle since that huge amount of water would have its own local
climatic effects and would make roads totally useless at
temperatures below freezing. Foreseeable but ignored consequences
abound.
Petrophysics, with other geosciences, can play
a role in finding and evaluating new naturally occurring hydrogen
resources. Current production is by reforming of methane,
electrolysis of water, or pyrolysis of methane. Petrophysics will
play a major role in locating these raw materials if the hydrogen
economy actually takes off.

The Colours of Hydrogen: green if produced from 100% renewables;
black, brown, or grey if coal or methane is used; blue if CCS is
added, gold or white if source is naturally occurring. (Image from
World Economic Forum, from 2022 talk by Emanuele Taibi)

The Green Hydrogen Transition (Image courtesy International
Renewable Energy Agency)
To produce enough Green Hydrogen to displace fossil fuels, we need
to increase renewable electrical energy output by a factor of 1000,
probably much more. And drill and complete unknown thousands of deep
water wells, plus build a desalinization plant for each electrolysis
plant. Why? Most of the fresh water needed for electrolysis is
already allocated to human and agricultural use.
It might be better to electrify transport and
use heat pumps for HVAC, and avoid the H2 middleman. This leaves
about 40% of current carbon emissions to be fixed – the carbon-heavy
industrial heartland to decarbonize with Green Hydrogen. As hydrogen
technology improves, the timing might just work out for all those
2050 targets that governments have made.
HYDROGEN PRODUCTION
There are over 200 chemical reactions that can produce
hydrogen, some dating back 150 years or so. None could be considered
“Green”. About 48% of commercial bulk hydrogen is produced by the
Steam Reforming Method (SRM), using natural gas as a feedstock, with
CO2 release to the atmosphere, or with carbon capture and storage
(CCS) to mitigate greenhouse gas (GHG) emissions.
Another large source is as a byproduct of the
manufacture of ammonia, methanol, and other industrial chemicals. A
tiny fraction is from electrolysis of water or pyrolysis of methane.
The 2015 discovery of naturally occurring
hydrogen in Mali has broadened the search for clean green sources.
HYDROGEN PRODUCTION
FROM METHANE USING STEAM REFORMING
The most common is reacting water, in the form of
super-heated steam (700 – 1100 C), with methane to form carbon
monoxide,, which in turn causes the removal of hydrogen from the
methane. The water vapor is then reacted with the carbon monoxide to
oxidize it to carbon dioxide, turning the water into hydrogen. The
process is called Steam Reforming, also known as the Bosch process.
The chemistry is:
1: CH4 + H2O → CO + 3 H2
2: CO + H2O → CO2 + H2
This reaction is favoured at low pressures but
is usually conducted at high pressures (2.0 MPa). This is because
high pressure H2 is the most marketable product, and pressure swing
adsorption (PSA) purification systems work better at higher
pressures. The product mixture is known as "synthesis gas" because
it is often used directly for the production of methanol and related
compounds.
HYDROGEN PRODUCTION FROM ELECTROLYSIS OF WATER
When a direct current is run through water, oxygen forms at the
anode (+) while hydrogen forms at the cathode(-). Typically the
cathode is made from platinum or another inert metal. While this a
proven technology, it supplies only 5% of World demand for hydrogen.
The method presumes that an adequate supply of
unallocated fresh water, (or desalinated sea water or medium, depth
oilfield brine) and a source of unallocated electricity can be
found. In many areas, fresh water is already in short supply and
additional draws on surface or near surface water may be impossible.
Deeper sources may also be restricted. See “Analyzing Water Wells”
to learn how to locate potential underground sources of water.
The chemistry electrolysis is pretty simple:
3: 2 H2O + electricity → 2 H2 + O2 + heat
Theoretical efficiency (electricity used vs.
energetic value of hydrogen produced) is between 88 – 94% with no
impurities in the water, much less if desalinization is needed.
Energy cost of co compression, storage, and transportation to market
are also not included3.
HYDROGEN PRODUCTION FROM METHANE PYROLYSIS
Natural gas (methane) pyrolysis is a one-step process that
produces no greenhouse gases. Developing volume production using
this method is the key to enabling faster carbon reduction by using
hydrogen in industrial processes, fuel cell electric heavy truck
transportation, and in gas turbine electric power generation.
Pyrolysis is achieved by having methane (CH4)
bubbled up through a molten metal catalyst containing dissolved
nickel at 1,070 C. This causes the methane to break down into
hydrogen gas and solid carbon, with no other byproducts (except
those from maintaining the reactor at the high temperature
required).
The chemistry is deceptively simple, but
implementation is tricky.
4: CH4 + heat + catalyst → C + 2 H2
The industrial-quality solid carbon may be
sold as manufacturing feedstock or permanently landfilled, it is not
released into the atmosphere and there is no ground water pollution
in the landfill.
Methane pyrolysis is in development and
considered suitable for commercial bulk hydrogen production,
assuming low cost methane is available as both feedstock and heat
source. Further research continues in several laboratories and at
least one pilot project.
NATIVE HYDROGEN FROM RESERVOIR
ROCKS
Conventional wisdom says that hydrogen gas does not occur
naturally in convenient reservoirs like oil and natural gas, because
the small molecules could escape too easily. This is not the case,
as a hydrogen reservoir is being exploited in the region of
Bourakebougou in Mali, producing electricity for the surrounding
villages.
Discovered in 2015 while drilling for water,
natural hydrogen blew out with the artesian water. Analysis of the
well Bougou-1 found the gas had a concentration of 98% pure
hydrogen, with traces of methane, nitrogen, and helium. This is the
purest naturally occurring hydrogen ever discovered.
Further exploratory wells were drilled and
analyzed, including two 2500 meter fully cored stratigraphic holes,
resulting in a second natural hydrogen gas field.
The hydrogen is trapped in 5 reservoir layers,
each sealed by a lava flow. The hydrogen molecule is so small, it is
possible that only unfractured igneous or evaporite minerals can
form the impermeable seal needed for hydrogen.
This is where petrophysics cones to the
rescue. Take a peak under the rug and see what might be waiting
below all those salts, anhydrites, and volcanics you drilled through
over the last 70 years. No, it won’t be that easy as you probably
need a deep-seated source and a migration path – well logs can help
there too.
It’s time for a paradigm shift for hydrogen!
Some scientists believe gas
generation will continue for thousands of years, sustainably
decarbonising the local community (who did not have much of a carbon
footprint to begin with. This is highly speculative as it may have
taken millions of years for the gas to migrate and accumulate from
deep source rocks to these reservoirs. There are at least 7 possible
mechanisms for the generation of hydrogen discussed in the reference
paper.

Stratigraphic sequence of Mali natural hydrogen discovery

Cross-section of Mali natural hydrogen discovery
Reference:
“On generating a geological model for hydrogen gas in the southern
Taoudeni Megabasin, Bourakebougou area, Mali” ACS Letters, 2016
Denis Briere and Tomas Jerzykiewicz, Chapman Consulting, Calgary AB
Canada
https://doi.org/10.1190/ice2016-6312821.1
NATIVE HYDROGEN
FROM SERPENTINIZATION REACTIONS
The hydrogen in the above example may have come from a
newly discovered iron-rich source at a moderate depth, or from a
much deeper and hotter source caused by serpentinization.
Serpentinization is a form of low temperature
metamorphism driven largely by hydration and oxidation of olivine
and pyroxene, creating serpentine minerals brucite, and magnetite.
Under the unusual chemical conditions accompanying serpentinization,
water is the oxidizing agent, and is itself reduced to hydrogen.
This leads to further reactions that produce rare iron group native
element minerals, such as awaruite and native iron, methane, and
other hydrocarbon compounds, and hydrogen sulphide.
During serpentinization, large amounts of water are absorbed into
the rock, increasing the volume, reducing the density and destroying
the original structure. The density changes from 3.3 to 2.5 gm/cc
with a concurrent volume increase on the order of 30 – 40%. The
reaction is highly exothermic and rock temperatures can be raised by
about 260 °C, providing an energy source for formation of
non-volcanic hydrothermal vents.
Hydrogen is produced during the process of
serpentinization. In this process, water protons (H+) are reduced by
ferrous (Fe2+) ions provided by fayalite (Fe2SiO4). The reaction
forms magnetite (Fe3O4), quartz (SiO2), and hydrogen (H2).
5: 3 Fe2SiO4 + 2 H2O → 2 Fe3O4 + 3 SiO2 + 3 H2 + heat
fayalite + water → magnetite + quartz + hydrogen
Laboratory studies of serpentinization at high
temperature and pressure show how methane could be produced, lending
some credence to deep-seated gas and oil generation and migration.
6: 18 Mg2SiO4 + 6 Fe2SiO4 + 26 H2O + CO2 → 12 Mg3Si2O5(OH)4 +4 Fe3O4
+ CH4
forsterite + fayalite + water + carbon dioxide → serpentine +
magnetite + methane
My 1954 grade 9 chemistry class didn’t get
much past 2H2 + O2 → 2 H2O, but equation 6 looks OK to me.
Ocean seeps show both hydrogen and methane
emissions. We just have to find them onshore, complete with
reservoir and seal, as in the Mali example. There are more than 100
published reports of natural hydrogen seeps on land in a dozen
countries, treated as curiosities across many years. Maybe they will
lead to a new industry, just as the oil seeps of antiquity did.
Reference: Wikipedia
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